Abstract
The state-of-the-art design criteria for High Frequency (HF) Radio Frequency IDentification (RFID) cards at 13.56 MHz depend on the choice of a resonance frequency and a quality factor of the card. Our investigations show that these values are a result of the Integrated Circuit (IC)’s non-linearity and its dynamic range. We describe our accurate method for calculating the IC’s circuit model during loaded and unloaded states. The dynamic range is identified where the IC is capable of achieving load modulation for all basic bit rates (106—848 kbit/s). The calculated IC’s circuit model is simulated and compared to measurements showing good agreement. We formulate a constrained minimization problem based on the IC’s circuit model, its dynamic range, including the entire card’s parasitics, as well as loading effects from the reader side. The problem’s solution is the optimum inductance for the card’s coil that renders a standard-compliant HF RFID card. A prototype card is manufactured based on the optimum inductance and we show that it passes the standardized tests and operates for all basic bit rates within the field intensity range from 1.5 to 7.5 A/m, as specified.
Highlights
The High Frequency (HF) Radio Frequency IDentification (RFID) cards are composed of two components: a coil and an Integrated Circuit (IC) containing a microcontroller and the radio interface
SUMMARY AND CONCLUSION We have demonstrated that designing HF RFID cards based on a maximum power transfer criterion alone is not suitable, as it does not render a standard-compliant card
We have shown that the main design parameter is the IC’s delivered voltage, which is limited by the IC’s non-linear behavior in addition to the IC’s dynamic range
Summary
In [21], we presented an approach to determine the loaded resistance based on the magnitude of the IC’s voltage and using the VNA to measure the magnitude and phase of the source voltage Vs. In this work, we use a different approach through simultaneously measuring the current IIC = I2 and voltage VIC at the IC’s terminals, so no need to use a VNA. We use a different approach through simultaneously measuring the current IIC = I2 and voltage VIC at the IC’s terminals, so no need to use a VNA This approach is simple to determine the loaded resistance of the IC, both magnitude and phase information are required.
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